Male stag beetles have enlarged mandibles that are used for fighting other males to control territory. The mandibles are long with powerful muscles that allow them to securely grip an opponent and lift him off the ground. Male stag beetles also have a thick hard cuticle to protect them from damage during their battles. The force that the beetle Cyclommatus metallifer can generate has been estimated* and it is capable of creating enough stress on a manidble to break or damage it. Yet stag beetles are rarely observed to damage their mandibles during a battle. Why?

The mandibles of stag beetles have sensors that communicate which portions of the mandible are engaged and the stress that is applied. The stag beetle uses information from the sensors in the madibles to adjust the muscular force. The tips are often thinner than the base and the stress is greatest. If only the tips are engaged, the beetle applies less force to his mandibles than if the more robust mid section of the mandible is enaged. Thus, the beetle adjusts the muscular force on the madibles to balance the grip on the opponent with the need to avoid damage.

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About jjneal

Jonathan Neal is an Associate Professor of Entomology at Purdue University and author of the textbook, Living With Insects (2010).
This blog is a forum to communicate about the intersection of insects with people and policy. This is a personal blog.
The opinions and materials posted here are those of the author and are in no way connected with those of my employer.